From Early Origins. When and Why does Asthma Develop?

Childhood asthma is an enigmatic condition which can develop in early or late childhood and thereafter persist or remit. Asthma has a complex phenotype whose aetiology is far from straight forward and many factors have been implicated. Genetic influences are widely accepted as important and thought to contribute towards as much as 50% of the risk for developing asthma. Environmental factors are also important and include antenatal and postnatal exposures to tobacco smoke, dietary factors and infective agents (including bacterial lipopolysaccharide). Large studies have demonstrated how pairings of several gene-environment combinations produce asthma; the heterogeneity of asthma may be explained by interactions between different combinations of genes and environmental factors each of which has a small-moderate influence on the outcome. The important gene environment interactions almost certainly occur in early life. A model is emerging where antenatal programming is followed by postnatal airway remodelling, driven by environmental exposures in genetically-susceptible individuals during critical stages of development. Intervention studies have confirmed the complexities of asthma pathogenesis. Future intervention studies will lead to better understanding of asthma pathogenesis and more importantly, to prevent this common condition.